---
title: sort-sets
description: Ensure your sets are sorted. Improve readability and maintain consistent code with this ESLint rule
shortDescription: Enforce sorted Set elements
keywords:
  - eslint
  - sort set
  - eslint rule
  - coding standards
  - code quality
  - javascript linting
  - set sorting
---

import CodeExample from '../../components/CodeExample.svelte'
import CodeTabs from '../../components/CodeTabs.svelte'
import dedent from 'dedent'

Enforce sorted set values.

By keeping sets sorted, developers can quickly scan and verify the values, making the code more predictable and reducing the likelihood of errors. This practice simplifies debugging and enhances the overall clarity of the codebase.


## Try it out

<CodeExample
  alphabetical={dedent`
    const getProductCategories = (product) => {
      let electronics = new Set([
        'Drone',
        'Headphones',
        'Keyboard',
        'Laptop',
        'Monitor',
        'Mouse',
        'Router',
        'Smartphone',
        'Smartwatch',
        'Tablet',
      ])
      let accessories = new Set([
        'Adapter',
        'Case',
        'Charger',
        'Screen Protector',
        'Cable',
        'Battery',
        'Memory Card',
      ])
      if (electronics.has(product.name)) {
        return 'Electronics'
      } else if (accessories.has(product.name)) {
        return 'Accessories'
      }
      return 'Unknown'
    }
`}
  lineLength={dedent`
    const getProductCategories = (product) => {
      let electronics = new Set([
        'Smartphone',
        'Smartwatch',
        'Headphones',
        'Keyboard',
        'Monitor',
        'Laptop',
        'Router',
        'Tablet',
        'Drone',
        'Mouse',
      ])
      let accessories = new Set([
        'Screen Protector',
        'Memory Card',
        'Adapter',
        'Charger',
        'Battery',
        'Cable',
        'Case',
      ])
      if (electronics.has(product.name)) {
        return 'Electronics'
      } else if (accessories.has(product.name)) {
        return 'Accessories'
      }
      return 'Unknown'
    }
`}
  client:load
  lang="tsx"
  initial={dedent`
    const getProductCategories = (product) => {
      let electronics = new Set([
        'Mouse',
        'Drone',
        'Smartphone',
        'Keyboard',
        'Tablet',
        'Monitor',
        'Laptop',
        'Smartwatch',
        'Router',
        'Headphones',
      ])
      let accessories = new Set([
        'Memory Card',
        'Charger',
        'Cable',
        'Battery',
        'Screen Protector',
        'Case',
        'Adapter',
      ])
      if (electronics.has(product.name)) {
        return 'Electronics'
      } else if (accessories.has(product.name)) {
        return 'Accessories'
      }
      return 'Unknown'
    }
`}
/>

## Options

This rule accepts an options object with the following properties:

### type

<sub>default: `'alphabetical'`</sub>

Specifies the sorting method.

- `'alphabetical'` — Sort items alphabetically (e.g., “a” < “b” < “c”) using [localeCompare](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/localeCompare).
- `'natural'` — Sort items in a [natural](https://github.com/yobacca/natural-orderby) order (e.g., “item2” < “item10”).
- `'line-length'` — Sort items by code line length (shorter lines first).
- `'custom'` — Sort items using the alphabet specified in the [`alphabet`](#alphabet) option.
- `'unsorted'` — Do not sort items. [`grouping`](#groups) and [`newlines behavior`](#newlinesbetween) are still enforced.

### order

<sub>default: `'asc'`</sub>

Specifies whether to sort items in ascending or descending order.

- `'asc'` — Sort items in ascending order (A to Z, 1 to 9).
- `'desc'` — Sort items in descending order (Z to A, 9 to 1).

### fallbackSort

<sub>
  type:
  ```ts
  {
    type: 'alphabetical' | 'natural' | 'line-length' | 'custom' | 'unsorted'
    order?: 'asc' | 'desc'
  }
  ```
</sub>
<sub>default: `{ type: 'unsorted' }`</sub>

Specifies fallback sort options for elements that are equal according to the primary sort
[`type`](#type).

Example: enforce alphabetical sort between two elements with the same length.
```ts
{
  type: 'line-length',
  order: 'desc',
  fallbackSort: { type: 'alphabetical', order: 'asc' }
}
```

### alphabet

<sub>default: `''`</sub>

Used only when the [`type`](#type) option is set to `'custom'`. Specifies the custom alphabet for sorting.

Use the `Alphabet` utility class from `eslint-plugin-perfectionist/alphabet` to quickly generate a custom alphabet.

Example: `0123456789abcdef...`

### ignoreCase

<sub>default: `true`</sub>

Specifies whether sorting should be case-sensitive.

- `true` — Ignore case when sorting alphabetically or naturally (e.g., “A” and “a” are the same).
- `false` — Consider case when sorting (e.g., “a” comes before “A”).

### specialCharacters

<sub>default: `keep`</sub>

Specifies whether to trim, remove, or keep special characters before sorting.

- `'keep'` — Keep special characters when sorting (e.g., “_a” comes before “a”).
- `'trim'` — Trim special characters when sorting alphabetically or naturally (e.g., “_a” and “a” are the same).
- `'remove'` — Remove special characters when sorting (e.g., “/a/b” and “ab” are the same).

### locales

<sub>default: `'en-US'`</sub>

Specifies the sorting locales. Refer To [String.prototype.localeCompare() - locales](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/localeCompare#locales).

- `string` — A BCP 47 language tag (e.g. `'en'`, `'en-US'`, `'zh-CN'`).
- `string[]` — An array of BCP 47 language tags.

### [DEPRECATED] groupKind

<sub>default: `'literals-first'`</sub>

Use the [groups](#groups) option with the `literal` and `spread` selectors instead. Make sure to set this option to `mixed`.

Groups set elements by their kind, determining whether spread values should come before or after literal values.

- `mixed` — Do not group set elements by their kind; spread values are sorted together with literal values.
- `literals-first` — Group all literal values before spread values.
- `spreads-first` — Group all spread values before literal values.

### partitionByComment

<sub>default: `false`</sub>

Enables the use of comments to separate the members of sets into logical groups. This can help in organizing and maintaining large sets by creating partitions based on comments.

- `true` — All comments will be treated as delimiters, creating partitions.
- `false` — Comments will not be used as delimiters.
- `RegExpPattern = string | { pattern: string; flags: string}` — A regexp pattern to specify which comments should act as delimiters.
- `RegExpPattern[]` — A list of regexp patterns to specify which comments should act as delimiters.
- `{ block: boolean | RegExpPattern | RegExpPattern[]; line: boolean | RegExpPattern | RegExpPattern[] }` — Specify which block and line comments should act as delimiters.

### partitionByNewLine

<sub>default: `false`</sub>

When `true`, the rule will not sort the members of a set if there is an empty line between them. This helps maintain the defined order of logically separated groups of members.

```ts
let items = new Set([
     // Group 1
    'Drone',
    'Keyboard',
    'Mouse',
    'Smartphone',

    // Group 2
    'Laptop',
    'Monitor',
    'Smartwatch',
    'Tablet',

    // Group 3
    'Headphones',
    'Router',
  ])
```

Each group of elements (separated by empty lines) is treated independently, and the order within each group is preserved.

### newlinesBetween

<sub>type: `number | 'ignore'`</sub>
<sub>default: `'ignore'`</sub>

Specifies how to handle newlines between groups.

- `'ignore'` — Do not report errors related to newlines.
- `0` — No newlines are allowed.
- Any other number — Enforce this number of newlines between each group, and forbid newlines inside groups.

You can also enforce the newline behavior between two specific groups through the `groups` options.

See the [`groups`](#newlines-between-groups) option.

This option is only applicable when [`partitionByNewLine`](#partitionbynewline) is `false`.

### groups

<sub>
  type: `Array<string | string[]>`
</sub>
<sub>default: `[]`</sub>

Specifies a list of groups for sorting. Groups help organize elements into categories.

Each element will be assigned a single group specified in the `groups` option (or the `unknown` group if no match is found).
The order of items in the `groups` option determines how groups are ordered.

Within a given group, members will be sorted according to the `type`, `order`, `ignoreCase`, etc. options.

Individual groups can be combined together by placing them in an array. The order of groups in that array does not matter.
All members of the groups in the array will be sorted together as if they were part of a single group.

Predefined groups are characterized by a selector.

##### List of selectors

- `literal` — Array elements that are not spread values.
- `spread` — Array elements that are spread values.

#### Newlines between groups

You may place `newlinesBetween` objects between your groups to enforce the newline behavior between two specific groups.

See the [`newlinesBetween`](#newlinesbetween) option.

This feature is only applicable when [`partitionByNewLine`](#partitionbynewline) is `false`.

```ts
{
  newlinesBetween: 1,
  groups: [
    'a',
    { newlinesBetween: 0 }, // Overrides the global newlinesBetween option
    'b',
  ]
}
```

### customGroups

<sub>
  type: `Array<CustomGroupDefinition | CustomGroupAnyOfDefinition>`
</sub>
<sub>default: `[]`</sub>

Defines custom groups to match specific elements.

A custom group definition may follow one of the two following interfaces:

```ts
interface CustomGroupDefinition {
  groupName: string
  type?: 'alphabetical' | 'natural' | 'line-length' | 'unsorted'
  order?: 'asc' | 'desc'
  fallbackSort?: { type: string; order?: 'asc' | 'desc' }
  newlinesInside?: number
  selector?: string
  elementNamePattern?: string | string[] | { pattern: string; flags?: string } | { pattern: string; flags?: string }[]
}

```
A set element will match a `CustomGroupDefinition` group if it matches all the filters of the custom group's definition.

or:

```ts
interface CustomGroupAnyOfDefinition {
  groupName: string
  type?: 'alphabetical' | 'natural' | 'line-length' | 'unsorted'
  order?: 'asc' | 'desc'
  fallbackSort?: { type: string; order?: 'asc' | 'desc' }
  newlinesInside?: number
  anyOf: Array<{
      selector?: string
      elementNamePattern?: string | string[] | { pattern: string; flags?: string } | { pattern: string; flags?: string }[]
  }>
}
```

A set element will match a `CustomGroupAnyOfDefinition` group if it matches all the filters of at least one of the `anyOf` items.

#### Attributes

- `groupName` — The group's name, which needs to be put in the [`groups`](#groups) option.
- `selector` — Filter on the `selector` of the element.
- `elementNamePattern` — If entered, will check that the name of the element matches the pattern entered.
- `type` — Overrides the [`type`](#type) option for that custom group. `unsorted` will not sort the group.
- `order` — Overrides the [`order`](#order) option for that custom group.
- `fallbackSort` — Overrides the [`fallbackSort`](#fallbacksort) option for that custom group.
- `newlinesInside` — Enforces a specific newline behavior between elements of the group.

#### Match importance

The `customGroups` list is ordered:
The first custom group definition that matches an element will be used.

Custom groups have a higher priority than any predefined group.

## Usage

<CodeTabs
  code={[
    {
      source: dedent`
        // eslint.config.js
        import perfectionist from 'eslint-plugin-perfectionist'

        export default [
          {
            plugins: {
              perfectionist,
            },
            rules: {
              'perfectionist/sort-sets': [
                'error',
                {
                  type: 'alphabetical',
                  order: 'asc',
                  fallbackSort: { type: 'unsorted' },
                  ignoreCase: true,
                  specialCharacters: 'keep',
                  groupKind: 'literals-first',
                  partitionByNewLine: false,
                  newlinesBetween: 'ignore',
                  useConfigurationIf: {},
                  groups: [],
                  customGroups: [],
                },
              ],
            },
          },
        ]
      `,
      name: 'Flat Config',
      value: 'flat',
    },
    {
      source: dedent`
        // .eslintrc.js
        module.exports = {
          plugins: [
            'perfectionist',
          ],
          rules: {
            'perfectionist/sort-sets': [
              'error',
              {
                type: 'alphabetical',
                order: 'asc',
                fallbackSort: { type: 'unsorted' },
                ignoreCase: true,
                specialCharacters: 'keep',
                groupKind: 'literals-first',
                partitionByNewLine: false,
                newlinesBetween: 'ignore',
                useConfigurationIf: {},
                groups: [],
                customGroups: [],
              },
            ],
          },
        }
      `,
      name: 'Legacy Config',
      value: 'legacy',
    },
  ]}
  type="config-type"
  client:load
  lang="tsx"
/>

## Version

This rule was introduced in [v3.4.0](https://github.com/azat-io/eslint-plugin-perfectionist/releases/tag/v3.4.0).

## Resources

- [Rule source](https://github.com/azat-io/eslint-plugin-perfectionist/blob/main/rules/sort-sets.ts)
- [Test source](https://github.com/azat-io/eslint-plugin-perfectionist/blob/main/test/sort-sets.test.ts)
